The invention relates to a gyroscope having a sleeve-shaped gyro rotor and a stator located inside the gyro rotor, in which the gyro rotor is mounted on both sides of the stator through ball bearings on an axle rigidly affixed to the stator.
Such gyroscopes serve as attitude reference instruments and are used for stabilization and navigation purposes. With a gyro in the form of a synchronous motor the stator comprises a rotor laminated stack with squirrel cage rods and squirrel cage rings. With a gyro in the form of a synchronous motor a hysteresis ring is provided correspondingly. Such gyroscopes must be manufactured with high precision, in order to avoid, for example, a drift, i.e., a slow deviation of the gyro spin axis from its original position.
With prior art gyroscopes of the type mentioned hereinbefore the rotor is composed of a plurality of parts. Usually the rotor comprises a rotor ring acting as a gyrowheel. This ring is conventionally composed of two halves. The inner surface of the rotor ring supports the rotor laminated stack. This rotor ring is mounted on the axle of the stator through bearing plates and a separate ball bearing mounted in the bearing plate. Generally the individual parts are made of different materials. With such a construction the manufacturing tolerances will add up. In addition, the dimension may vary due to different thermal dilation of the parts.
In other prior art gyroscopes (U.S. Pat. No. 3,248,952) the gyro rotor is not mounted directly on the axle of the stator but independently thereof in the gyro housing. With such a design, additional tolerances with regard to the alignment of the gyro rotor and the stator will result.
Furthermore, a gyro is known in which the rotor lamination is set into a sleeve-shaped rotor ring which has a straight cylindrical through bore. The rotor is mounted on both sides on two aligned pins provided on a frame or, through ball bearings and bearing plates. The stator of the gyro is supported between the two pins through resilient metal diaphragms. Also with this prior art design there will be considerable problems of manufacturing technique, for example, due to the fact that the two pins separately attached to the frame have to be in exact alignment with each other.
It is the object of the invention to provide a gyroscope of the type defined in the beginning which can be manufactured with high precision with conventional manufacturing processes, in which the cumulative number of tolerances involved can be kept small and which permits easy assembly of the gyroscope.
In accordance with the invention, this object is achieved in that the gyro rotor forms a substantially solid annular part comprising a rotor ring and a motor drive member and has a cylindrical through bore and plane end faces normal to the axis of this through bore and that the ball bearings, having their inner rings seated on the axle of the stator, fit with a cylindrical peripheral surface directly into the through bore and are trued by radial flanges relative to the respective end faces.
In the design of the invention the gyro rotor behaves substantially like a solid part which may be manufactured with correspondingly high precision. This part has a straight cylindrical through bore. The plane end faces of the rotor are machined in accordance with this through bore. The ball bearing seats on the axle of the stator and the circumferential surface of the stator laminated stack can be machined in similarly precise manner. Then the ball bearing, manufactured with high precision, ensures the exactly aligned arrangement of the gyro rotor relative to the stator. There are substantially only four parts, namely, the stator, the rotor and the two ball bearings whereby the number of tolerances which can add up is at a minimum. In order to disassemble the gyro thus constructed, it is only necessary to pull the ball bearings axially off the axle of the stator. Then the stator can be pulled out of the straight, cylindrical through bore without any disassembly of the gyro rotor. The assembly can be effected in the same way, the mutual re-alignment of the parts being ensured.
A method for manufacturing a gyro constructed in accordance with the invention is characterized in that the inner parts of the gyro rotor are manufactured with a machining allowance and are shrink fitted into a cylindrical annular case member to form a solid blank, that subsequently the through bore of this blank is machined accurately to a size appropriate for the accommodation of the stator with allowance for the air gap as well as for the accommodation of the outer ring of the ball bearing, that subsequently the end faces of the gyro rotor are machined accurately in a machining procedure orienting itself by use of the machined through bore, that a stator laminated stack is heat fitted on the axle of the stator and ball bearing seats are machined with high accuracy on the axle on both sides of the stator laminated stack, and that, after the stator has been inserted into the through bore, the ball bearings are put onto the axle from both sides with their inner rings on the ball bearing seats and the bearings are set into the through bore of the gyro rotor with the cylindrical circumferential surfaces of the outer rings of the bearings seated upon the rotor, and the bearings eventually are preloaded by screwing screw-down nuts onto the axle of the stator.